The present invention relates in general to hydraulic pressure transformers, and in particular to a hydraulically driven axial piston pump of the type having a first part including an intake port, a discharge port and a set of at least three hydraulically driven cylinder-and-piston units each defining a control opening for admitting and releasing a driving liquid, a second part containing a discharge chamber connectable to a consumer, a suction chamber for a driven medium, a set of plungers arranged in the suction chamber, suction valves and pressure valves arranged in the second part and cooperating with respective plungers, and piston rods connecting the pistons in the cylinder-and-piston units to the plungers.